The present invention relates to dual fuel single injector nozzles for use with coal fired diesels.
In coal fired diesels it is desirable to provide as the first charge in a cycle a small quantity of diesel fuel referred to as the pilot charge. The pilot charge fires very quickly increasing chamber pressure and temperature resulting in more rapid ignition of the coal/water slurry injected immediately following the pilot charge. Presently, a separate injector can be provided for injecting pilot fuel and a separate coal/water slurry injector can be provided to add the slurry. A stratified single nozzle injector can alternatively be used. A stratified single nozzle injector has coal/water slurry and pilot fuel in the same chamber of the injector with the coal/water slurry and fuel oil separating or stratifying. When the pilot fuel and slurry are injected into the combustion chamber, pilot fuel is in the lower portion of the chamber and is introduced first into the combustion chamber. The performance of the stratified charge injector is better than that of the separate pilot fuel and coal/water slurry injectors because of the better heating of the coal/water slurry which is delivered to the same spray pattern location as the previously ignited pilot fuel. However there are several drawbacks to stratified charge nozzles. The main problem is that over time wear in the moving parts of the nozzle caused by the coal/water slurry increases the amount of pilot fuel introduced with each firing and control over the ratio of pilot fuel to coal/water slurry is lost.
It is an object of the present invention to provide a dual fuel single injector nozzle for use with slurry fuels.
It is a further object of the present invention to provide a dual fuel single injector nozzle that provides a precise amount of pilot fuel prior to the introduction of the coal/water slurry.
It is a further object of the present invention to provide a dual fuel single injector nozzle having a purged valve seat.